1. Field of the Invention
The invention relates generally to a pavement life extension method that combines a material, repair methods and equipment to accomplish the overall goal of extending the useful life of different types of transportation and vehicular pavement.
2. Background
In the case of other systems that use non-asphaltic combinations to overlay pavements, the material that is used requires far too much water which dilutes the latex emulsion beyond its limits thereby destroying the latex's binding and adhesive qualities. Another known product uses a cement/sand blend with too much cement. This product blends two parts 80 to 100 mesh mason sand with one part Type I Portland cement. This blend is far too rich in cement which in turn bleeds lime for an extended period of time and is also far too brittle (low plasticity) due to the large quantity of cement and not enough aggregate (sand). Other systems use equipment that is not proven in the marketplace or that is specifically designed for asphalt/petroleum based products. This renders a finished product that is aesthetically unacceptable and physically unstable.
Examples of Past Polymer Composition Pavement Overlays:
U.S. Pat. No. 5,244,304 Is directed to a paving composition including a cement binder, a dispersible latex polymer binder and a mineral aggregate filler such as sand.
U.S. Pat. No. 4,430,463 discloses a flexible acrylic polymer Portland cement coating composition having unusual shear bond (adhesive) characteristics and unusually high abrasion and heat resistance which incorporates sand, Portland cement, acrylic polymer, propylene glycol and a defoamer.
U.S. Pat. No. 4,714,507 sets forth a surface coating agent and method for applying the coating to a road surface. The surface coating agent comprises a principal ingredient consisting mostly of cement silicon dioxide, generally in the form of silica sand, iron oxide, zinc oxide, and glycine and a composite polymer emulsion composed mainly of carboxy-modified styrene-butadiene polymer, wherein the ratio of principal ingredient to the composite polymer is 2.0 to 6.0:1.
In addition, owing to the high cost of fossil fuels, a number of pavement maintenance products have become not only unsafe with respect to the environment, but have also become very expensive for many end users. Especially with respect to the usable life expectancy of these antiquated petroleum based materials, many end users, predominantly Federal, State and Aviation agencies, have been forced to investigate other products that would not only meet their budgetary constraints but also meet many other requirements centered around environmental issues, Solar Heat Reflectivity, comparable durability and rapid re-access to the assets with which the materials are placed. With regards to asphalt pavement; water, UV, hydrocarbons and extended spans between repaving or re-sealing has caused severe oxidation and raveling to many roads, bridges, aviation pavement/operating surfaces, parking lots and vehicular service areas to a point to where expensive reconstruction is the only option that for the foreseeable future is unaffordable. Once the sun begins to evaporate the fine oils that hold the binder together, the small aggregate and sand begin to loosen and gravitate to the road shoulder or curb. At that point all that is exposed is the ¼ to ½ inch polished rock and larger aggregate that decreases the coefficient of friction. This condition combined with wet weather and oils that naturally leak from passing vehicles can cause an extremely dangerous vehicular situation.
Coal Tar, a by-product of the coal industry, is a very well known and effective topical deterrent to asphalt oxidation, exposure to UV and water as well as fuel and chemicals. However, the negative aspects of its use has begun to outweigh its advantages. The product is considered to be very hazardous to human and animal exposure and animate and inanimate objects. Coal Tar sealers have a significant “tracking” effect that destroys interior flooring to buildings and businesses. Coal Tar also possesses a very strong odor that remains with the surface for weeks at a time. With regards to human exposure, applicators are exposed to caustic fumes that cause chemical skin burns and has also been believed to cause cancer in certain studies. Coal Tar has been banned from usage in a number of states due to PAH's, a chemical by-product of coal tar that is extremely harmful to humans, animals and the overall environment. Its continued use in a number of other states is based on the low cost of the material and its placement.
Another asphalt-based product that has seen a wide range of usefulness is a paving concept called Chip Seal or Chip Sealing. This pavement concept is widely used on county roads due to the low cost and low level of commercial traffic. The chip seal method is constructed of a heavy hot liquid asphalt tack material that is sprayed and sometimes spread with a slurry placement machine. The heavy hot asphalt tack material is then covered with limestone ranging in sizes from No. 88 (⅛″) to No. 57 (1.5″) and a blend of both and all between from a tandem dump truck and spread with a tractor or motor grader. The composition is then rolled with a 14 ton vibratory roller and allowed to cool and harden. Once hard and set, the road is then broomed several times with a commercial street sweeper to remove any loose aggregate. The main deficiency with this pavement maintenance technique is that within a very short time the aggregate begins to loosen and dislodge from the asphalt tack material. As vehicles ride over the surface more stones dislodge and are thrown up into oncoming or following vehicular traffic. This causes an exponential number of cracked and broken windshields and in many cases accidents caused by a build up or concentration of loose aggregate in the road center or edges. As most county roads are only 18 feet to 20 feet wide, there is very little margin for error once this condition evolves into reality. However, due to the growing concerns and hazardous events surrounding this concept, most counties have been forced to overlay this type of surface with a 1.5″ asphalt overlay to rectify the liability chip seal roads create.
Concrete on the other hand, has predominantly been a very expensive alternative to asphaltic pavement construction. When crude oil prices were around $20.00 to $30.00 a barrel, asphalt remained the sub-base and surface of choice for public and private roads, parking lots and other transportation wearing surfaces. Concrete for the first time in its history has become less expensive than asphalt for the construction of many transportation related surfaces. Its durability, strength and resistance to UV, water, fuel and chemical spillage is incomparable to asphalt. However, full-depth concrete also suffers from a number of issues related to structural conditions, extreme chemical exposure and ride-ability. First of all, concrete is not as smooth a riding surface as asphalt. The construction process is very time consuming causing driver anxiety. Concrete tends to heave in a true plane in expansive soil regions causing vertical separations at each expansion joint. (Asphalt, on the other hand, tends to roll with the heaving soil and crack when its tensile strength is breached). This is a very dangerous traffic condition for both surfaces which requires planing of the uneven joint to smooth the transition from one panel to the next or the expensive process of panel replacement. Over an extended period of time the top ¼″ “cream” of the concrete wearing surface begins to erode due to traffic, water and basic deterioration. At this point the aggregate becomes exposed which in turn substantially lowers the coefficient of friction for not only concrete roads but bridge decks. The transition from one type of pavement surface to a worn bridge deck surface can be extremely dangerous in wet weather. In severe cold weather conditions, depending on the aggregate used in the mix design, the aggregate can freeze in the top 1″ of the concrete profile and cause the aggregate to burst due to the microscopic water polyps inside the concrete aggregate. This condition is referred to as “pop-outs” that can range from ½″ to 2″ in diameter which in turn can and will begin an erosion and concurrent spalling process. As for concrete bridge decks, there has historically been only one alternative for repairing many of the problems that plague old bridge decks . . . reconstruction. This reconstruction process is not only time consuming but also very expensive to State DOT (Dept. of Transportation), budgets. Many of the problems that are systemic with older concrete bridge decks are loss of friction due to exposure of the polished rock aggregate, concrete spalling and substantial aggregate pop-outs. These conditions are responsible for a large number of vehicular accidents in many states that suffer DOT budgetary problems because funds are not available for total reconstruction. Also, older bridge decks, especially those with wood/timber pilings, (characteristic of county roads), cannot withstand the additional weight load of full depth concrete overlays to repair and improve the ride-ability of these older bridge decks.
In an effort to resolve the weaknesses of these pavement materials and structural deficiencies, there have been a number of products that have been introduced to the market to try and minimize, slow down and ultimately stop the conditions and problems that these pavement commodities create with limited to moderate success. With this background synopsis it can be observed that there is a need for a highly evolved polymer modified cement micro overlay formulation, installation and repair method which overcomes the weaknesses of asphalt degradation, chip seal deterioration, coal tar sealer hazards and concrete road and bridge deck spalling, pop-out and joint repair. These evolutionary developments in addition to a rapid turn-around with minimal interruption to vehicular traffic are the essence of this invention.